A nuclear reactor produces electrical power by heating water in a reactor pressure vessel that contains a nuclear fuel core in order to generate steam which is used in turn to drive a steam turbine. Various components and structures in a nuclear reactor are examined periodically assess its structural integrity and determine the need for repair. Ultrasonic inspection is a known technique for detecting cracks in nuclear reactor components. The inspection areas in the nuclear reactor may have limited access and therefore, difficult to assess using an inspection tool. For example, the core shroud welds are periodically assessed for stress corrosion cracking. The presence of stress corrosion cracking can diminish the structural integrity of the core shroud. However, the core shroud is difficult to access. Installation access is limited to the annular space between the outside of the shroud and the inside of the reactor pressure vessel, between adjacent jet pumps. Scanning operation access is additionally restricted within the narrow space between the shroud and jet pumps.
Further, the inspection areas in a nuclear reactor can be highly radioactive and can pose safety risks for personnel working in these areas. Thus, inspection of these areas for the most part can require a robotic device which can be installed remotely and operated within the narrowly restricted space.
Inspecting and repairing nuclear reactors, such as boiling water reactors, typically consist of manually controlled poles and ropes to manipulate servicing devices and/or positioning of these devices. During reactor shut down, servicing of some components require installation of inspection manipulators or devices 30 to 100 feet deep within reactor coolant. Relatively long durations are required to install or remove manipulators and can impact the plant shutdown duration. In addition, different inspection scopes can require several manipulator reconfigurations requiring additional manipulator installations and removals. The long durations cannot only impact plant shutdown durations, but also increase personnel radiation and contamination exposure.
Plant utilities have a desire to reduce the number of manipulator installations and removals to reduce radiological exposure as well as cost and plant outage impact. This invention allows the number of reconfigurations, installations and removals to be minimized. It is contemplated that if utilized on currently available manipulators, approximately one-half of the configurations may be eliminated.